To acquire an absolute angle of a rotating object, there is a conventionally used method of detecting an encoded pattern with a sensor having a high resolution, such as an absolute encoder.
FIGS. 12(a) to (c) are explanatory diagrams showing an example of such a conventional method of detecting the absolute angle. Of these, FIG. 12(a) is a side view of a substantial part of the encoder, FIG. 12(b) is a plan view of a disk of the absolute encoder, and FIG. 12(c) is an enlarged view of a part A in FIG. 12(b). As shown therein, an absolute encoder 60 has a pattern 62 which is a binary n-bit code cut into slits and encoded by angle formed on an absolute position detecting disk 61. Furthermore, a one-rotation detecting pattern 69 for detecting an origin is provided. In particular, the pattern encoded by angle is formed by a significantly advanced manufacturing technology.
There are also the following conventional technologies as to detection of the number of rotations and angle of rotation. To be more specific, there are a method of detecting the number of rotations by using multiple light sources for radiating light of different properties on an NMR apparatus (Patent Document 1 listed below), a method of changing a degree of monochromatic coloring on axial periphery and thereby knowing an axial displacement (Patent Document 2).
Patent Document 1: Japanese Patent Laid-Open No. 2001-215239, “Body of Rotation Detector”, Abstract, claims and FIG. 3
Patent Document 2: Japanese Patent Laid-Open No. 1-277704, “Rotation Axis Displacement Detector”, Abstract, claims and FIG. 1
As described above, in the conventional method of detecting the absolute angle, formation of a pattern encoded by angle requires a significantly advanced manufacturing technology, and so a body of rotation should be in a certain size or larger. As a characteristic of detection is influenced by positions and the like of the configured sensors and light sources, positioning thereof requires high accuracy and manufacturing involves considerable difficulties. Therefore, miniaturization and cost reduction of a detector is difficult. Furthermore, it is impossible detect a position on an XY plane.
Such a technical limit remains basically unsolved even in proposals indicated in the above-mentioned Patent Documents.
An object to be attained by the present invention is to provide a position detector and a detected element which are rid of the problems of the conventional technologies and capable of detecting an absolute angle of a rotating object and an absolute position on an XY plane by using a simpler configuration and an easier method, facilitating assembly of an apparatus, miniaturizing the apparatus and reducing costs thereof.